loop: Bug fix: vsync should not use channels on browsers (#259)

internal/loop/run.go

@@ -86,6 +86,12 @@ type GraphicsContext interface {
 	UpdateAndDraw(context *opengl.Context, updateCount int) error
 }
 
+type regularTermination struct{}
+
+func (e regularTermination) Error() string {
+	return "regular termination"
+}
+
 func Run(g GraphicsContext, width, height int, scale float64, title string, fps int) (err error) {
 	if currentRunContext != nil {
 		return errors.New("loop: The game is already running")
@@ -107,24 +113,41 @@ func Run(g GraphicsContext, width, height int, scale float64, title string, fps
 	n := now()
 	currentRunContext.lastUpdated = n
 	currentRunContext.lastFPSUpdated = n
+
+	if err := ui.CurrentUI().AnimationFrameLoop(func() error {
+		return currentRunContext.update(g)
+	}); err != nil {
+		if err == (regularTermination{}) {
+			return nil
+		}
+		return err
+	}
+	return nil
+}
+
+func (c *runContext) update(g GraphicsContext) error {
 	for {
 		e, err := ui.CurrentUI().Update()
 		if err != nil {
 			return err
 		}
 		switch e := e.(type) {
+		case ui.NopEvent:
+			return nil
 		case ui.ScreenSizeEvent:
 			if err := g.SetSize(e.Width, e.Height, e.ActualScale); err != nil {
 				return err
 			}
 			e.Done <- struct{}{}
+			continue
 		case ui.CloseEvent:
-			return nil
+			return regularTermination{}
 		case ui.RenderEvent:
 			if err := currentRunContext.render(g); err != nil {
 				return err
 			}
 			e.Done <- struct{}{}
+			return nil
 		default:
 			panic("not reach")
 		}
@@ -163,9 +186,9 @@ func (c *runContext) render(g GraphicsContext) error {
 	if err := g.UpdateAndDraw(ui.GLContext(), tt); err != nil {
 		return err
 	}
-	if err := ui.CurrentUI().SwapBuffers(); err != nil {
+	/*if err := ui.CurrentUI().SwapBuffers(); err != nil {
 		return err
-	}
+	}*/
 	c.lastUpdated += int64(tt) * int64(time.Second) / int64(fps)
 	c.frames++
 	return nil

internal/ui/event.go

@@ -14,6 +14,9 @@
 
 package ui
 
+type NopEvent struct {
+}
+
 type CloseEvent struct {
 }
 

internal/ui/ui.go

@@ -17,8 +17,8 @@ package ui
 type UserInterface interface {
 	Start(width, height int, scale float64, title string) error
 	Update() (interface{}, error)
-	SwapBuffers() error
 	Terminate() error
+	AnimationFrameLoop(f func() error) error
 	ScreenScale() float64
 	SetScreenSize(width, height int) (bool, error)
 	SetScreenScale(scale float64) (bool, error)

internal/ui/ui_glfw.go

@@ -251,17 +251,21 @@ func (u *userInterface) Terminate() error {
 	return nil
 }
 
-func (u *userInterface) SwapBuffers() error {
-	// The bound framebuffer must be the default one (0) before swapping buffers.
-	if err := glContext.BindScreenFramebuffer(); err != nil {
-		return err
+func (u *userInterface) AnimationFrameLoop(f func() error) error {
+	for {
+		if err := f(); err != nil {
+			return err
+		}
+		// The bound framebuffer must be the default one (0) before swapping buffers.
+		if err := glContext.BindScreenFramebuffer(); err != nil {
+			return err
+		}
+		if err := u.runOnMainThread(func() error {
+			return u.swapBuffers()
+		}); err != nil {
+			return err
+		}
 	}
-	if err := u.runOnMainThread(func() error {
-		return u.swapBuffers()
-	}); err != nil {
-		return err
-	}
-	return nil
 }
 
 func (u *userInterface) swapBuffers() error {

internal/ui/ui_js.go

@@ -29,12 +29,14 @@ type userInterface struct {
 	scale           float64
 	deviceScale     float64
 	sizeChanged     bool
-	contextRestored chan struct{}
-	windowFocus     chan struct{}
+	contextRestored bool
+	windowFocus     bool
 }
 
 var currentUI = &userInterface{
-	sizeChanged: true,
+	sizeChanged:     true,
+	contextRestored: true,
+	windowFocus:     true,
 }
 
 func CurrentUI() UserInterface {
@@ -46,16 +48,6 @@ func shown() bool {
 	return !js.Global.Get("document").Get("hidden").Bool()
 }
 
-func vsync() {
-	ch := make(chan struct{})
-	js.Global.Get("window").Call("requestAnimationFrame", func() {
-		// TODO: In iOS8, this is called at every 1/30[sec] frame.
-		// Can we use DOMHighResTimeStamp?
-		close(ch)
-	})
-	<-ch
-}
-
 func (u *userInterface) SetScreenSize(width, height int) (bool, error) {
 	return u.setScreenSize(width, height, u.scale), nil
 }
@@ -74,11 +66,11 @@ func (u *userInterface) ActualScreenScale() float64 {
 }
 
 func (u *userInterface) Update() (interface{}, error) {
-	if u.windowFocus != nil {
-		<-u.windowFocus
+	if !u.windowFocus {
+		return NopEvent{}, nil
 	}
-	if u.contextRestored != nil {
-		<-u.contextRestored
+	if !u.contextRestored {
+		return NopEvent{}, nil
 	}
 	currentInput.updateGamepads()
 	if u.sizeChanged {
@@ -102,12 +94,19 @@ func (u *userInterface) Terminate() error {
 	return nil
 }
 
-func (u *userInterface) SwapBuffers() error {
-	vsync()
-	for !shown() {
-		vsync()
+func (u *userInterface) AnimationFrameLoop(f func() error) error {
+	ch := make(chan error)
+	var ff func()
+	ff = func() {
+		if err := f(); err != nil {
+			ch <- err
+			close(ch)
+			return
+		}
+		js.Global.Get("window").Call("requestAnimationFrame", ff)
 	}
-	return nil
+	ff()
+	return <-ch
 }
 
 func (u *userInterface) FinishRendering() error {
@@ -151,14 +150,10 @@ func initialize() error {
 		<-ch
 	}
 	window.Call("addEventListener", "focus", func() {
-		if currentUI.windowFocus == nil {
-			return
-		}
-		close(currentUI.windowFocus)
-		currentUI.windowFocus = nil
+		currentUI.windowFocus = true
 	})
 	window.Call("addEventListener", "blur", func() {
-		currentUI.windowFocus = make(chan struct{})
+		currentUI.windowFocus = false
 	})
 
 	canvas = doc.Call("createElement", "canvas")
@@ -244,11 +239,11 @@ func initialize() error {
 
 	canvas.Call("addEventListener", "webglcontextlost", func(e *js.Object) {
 		e.Call("preventDefault")
-		currentUI.contextRestored = make(chan struct{})
+		currentUI.contextRestored = false
 	})
 	canvas.Call("addEventListener", "webglcontextrestored", func(e *js.Object) {
-		close(currentUI.contextRestored)
-		currentUI.contextRestored = nil
+		// TODO: Call preventDefault?
+		currentUI.contextRestored = true
 	})
 	return nil
 }

internal/ui/ui_mobile.go

@@ -98,8 +98,12 @@ func (u *userInterface) Update() (interface{}, error) {
 	return RenderEvent{chRenderEnd}, nil
 }
 
-func (u *userInterface) SwapBuffers() error {
-	return nil
+func (u *userInterface) AnimationFrameLoop(f func() error) error {
+	for {
+		if err := f(); err != nil {
+			return err
+		}
+	}
 }
 
 func (u *userInterface) SetScreenSize(width, height int) (bool, error) {